System and device for prolonging the life of current energized filamentary elements



R. C.'WUERTH 2,756,382 SYSTEM AND DEVICE FOR PROLONGING THE LIFE OF CURRENT ENERGIZED FILAMENTARY ELEMENTS July 24, 1956 Filed June 250, 1953 SYSTEM AND DEVICE FOR PROLONGING THE LIFE OF CURRENT ENERGIZED FILAMENTARY ELEMENTS Robert C. Wuerth, Philadelphia, Pa.

Application June 30, 1953, Serial No. 365,030

2 Claims. (Cl. 323-68) This invention relates to systems and devices for pro longing the life of devices such as electron tubes having current-receiving elements which when cold are subjected to severe shock by initial full energization. More particularly, the invention relates to systems and devices for effecting initially reduced energization of such elements to lessen or substantially eliminate the shock.

Experience has shown that the life of an electron tube is greatly shortened by premature burn-out of the filamentary element, employed either as the cathode or as the cathode heater, due to repeated severe shock caused by application of full energizing current to the element when it is cold. This is particularly serious in view of the present day extensive use of electron tubes in various fields. The television field alone uses a very great number of electron tubes, and since television receivers are now in wide use in homes and have largely supplanted radio receivers, the burn-out of tubes in television receivers directly affects almost everybody and is a source of annoyance and expense. Most failures of television receivers are due to tube burn-outs, and therefore prolongation of the life of television receiver tubes will greatly reduce the inconvenience and expense incident to tube burn-outs. While the present invention is not limited to television, it is particularly useful in respect thereto.

The principal object of this invention is to provide a simple and inexpensive system for overcoming the abovementioned objection.

Another object of the invention is to provide a simple device which may be manufactured and sold at low cost, and which requires only the insertion of a plug into a power outlet to put the device into operation.

A further object of the invention is to provide a device which is easily adjustable to vary the time interval of reduced energization of the supplied apparatus.

Other objects and features of the invention will be apparent from the following detailed description.

In the accompanying drawing,

Fig. l is a perspective view of a device embodying the invention;

Fig. 2 is a sectional view taken along line 22 of Fig. 1;

Fig. 3 is a sectional view taken along line 3-3 of Fig. 2;

Fig. 4 is an exploded perspective view of the elements comprising the thermostatic time delay arrangement employed in the device; and

Fig. 5 is a diagrammatic illustration of the electrical system.

Referring more particularly to the drawing, in the preferred form of the invention, there is provided a relatively small compact unit comprises a casing or housing 10, having a removable cover 11, within which the elements of the device are contained. Wall 12 of the casing is apertured to accommodate a conventional outlet recep tacle 13 which is held in place by means of a plate 14 secured to wall 12 by bolts 15, and an associated springretainer ring 16. The opposite wall 17 of the casing is nited States Patent Ofiice 2,756,382 Patented July 24, 1956 also apertured to accommodate a conducting cord 18 extending through a grommet 19 provided in the wall aperture. At the outer end of the conductor cord 18 is a conventional power receptacle plug 20.

Within the casing 10 are connections which provide a supply circuit extending to the receptacle 13, which circuit is shown in Fig. 5 and will be described later. A resistor 21 is mounted within the casing 10, as by means of spring clips 22 and 23 engaging the ends of the resistor and bolted to the wall 17. A lamp socket 24, to accommodate a lamp 25, is also mounted within the casing 10, as by means of a bracket 26 bolted to the wall 27. Also provided within the casing 10 is a thermostatic time delay switch arrangement now to be described.

An insulating plate 28 is fixedly mounted within the casing 19 as by means of supporting bolts 29. A substantially U-shaped bimetallic member 30 is mounted at the end portions of its legs on the insulating plate 28, as by means of rivets 31. This member has terminal extensions 32 to facilitate electrical connection thereto. At the bend of the U-shaped member, there is provided a contact 33. Also, mounted on the insulating plate 28 is a current-conductive spring arm 34 which is secured at one end to the plate 28 as by means of rivets 35, and which carries a contact 36 at its free end for cooperation with contact 33, these two contacts constituting a switch. A relatively rigid current-conductive arm 37 has its lower portion in engagement with the lower portion of arm 34 and is secured by the same rivets 35 which secure arm 34. The lower end of arm 37 is provided with a terminal extension 38 for connection of a conductor thereto. Thus, the terminal 38 effectively serves as a terminal for the switch arm 34 which is electrically connected to arm 37 through the rivets 35. The upper portion 39 of arm 37 is looped and is provided with threaded apertures to accommodate an adjusting screw 46. This screw engages arm 34 and serves to adjust contact 36 in relation to contact 33.

Referring now to Fig. 5, it will be seen that one of the supply conductors 18 is connected directly to one side of the receptacle 13. The other supply conductor is connected to one end of the resistor 21, the other end of which is connected to one of the legs of the U-shaped bimetallic member 30. The other leg of the U-shaped member is connected to the receptacle 13. The lamp 25 is connected in parallel relation with the resistor 21. The switch arm 34 is connected to the line end of resistor 21.

In using the device, for example in conjunction with a television receiver, it is merely necessary to insert the plug 20 into a power outlet, and to'insert the power supply plug of the television receiver into the receptacle 13. in operation, the contact 36 is stationary, and initially the contacts 33 and 36 are open. When the television receiver is turned on, current flows through the resistor 21 and lamp 25 in parallel and through the entire U-shaped bimetallic member 3d. The resistor 21 serves as a current-limiting impedance and reduces the current substantially below the full energization current. 1 course, the value of the resistor will depend upon the voltage and load and the extent to which it is desired to reduce the current. The current flowing through the U-shaped bimetal member 30 causes it to flex in a direction to move contact 33 toward contact 36. After a predetermined time interval, the contacts close and this short circuits both the resistor and lamp 25 and also one leg of the U-shaped member 30. The flow of full energization current through the other leg of member 30 maintains it in its flexed condition to keep contacts 33 and 356 closed. The short circuiting of the resistor 21 effects flow of full energizati-on current to the apparatus being supplied. The remaining leg of the bimetal member does not appreciably reduce the current 'blned thermomotive action of the two legs.

as it is of low resistance-compared with the current limiting resistor and filaments of the load.

It should be noted that each leg of the U-shaped bimetallic member is a thermomotive element, and initially the reduced energization current flows through both legs and is sufficient to flex member 38 *because of the com- When the contacts close, only one leg continues to function as a thermomotive element, but the full energization current flowing therethrough compensates for the effective removal of the other leg and maintains the switch contacts closed. It will be apparent, of course, that the substantially U shape-of the bimetal member may be in the form of a V, and in fact the bimetal member may take any suitable form.

The'time interval during which lessthan-full energizing current is supplied may be varied'by means of the adjusting screw 40. The lamp serves as an indicator, and a light-transmitting member 41 is provided on 'the cover 11 to provide a visual indication. Any form of window will serve the latter purpose, for example a simple aperture could be employed. An aperture 42 is provided in cover 11 in alignnlent'with the head of screw 40 so that a screw driver may be inserted to adjust the screw.

The use of the present device, e. g. with a television receiver, does not appreciably prolong the time required to bring the receiver to operative condition. Actual tests have shown that a period of about ten seconds is sufficient for the initial decreased energization, and the delay in operation of the receiver is only about five seconds. Further, actual test over a period of time has shown that,

with initial decreased energization of about one-half the full current for a period of about ten seconds, this-device 'will prolong the life of tubes to about three times their ordinary life.

While a preferred form-of the invention has been illustrated and described, the invention is not limited thereto but contemplates such other embodiments and modifications as may occur to those skilled in the art.

I claim:

1. A current-supply system for etieeting initially reduced energization of devices such as electron tubes, comprising a current-supply circuit, a current limiting impedance serially included in said circuit, whereby initially to eifect 'less-than-full energization of a supplied device, a current-conducting thermomotive member serially ineluded-in said circuit to receive current and connected to one side of said impedance, both ends -of the thermomotive member being supported on rigid supports 'fixed relative to one another, a normally-open switch comprising a stationary contact fixed relative to the ends of the thermomotive member and a contact electrically connected to an intermediate point of said member and movable thereby to engage said stationary contact upon current activation of said member, and a connection between said stationary contact and .a ,point of said circuit on the side of said impedance opposite the side to which said member is connected, whereby the closing of said switch short circuits said impedance and a portion of said member, whereupon substantially full energizing current is supplied to the supplieddevice and said switch is maintained in the short-circuiting position by the heating effect generated in 'the remaining portion'of said member by the increased current which flows therethrough, whereby-one portion of the thermomotive member is cooler than the other and whereby the cooler portion partially counteracts the forces acting on the hotter portion.

2. A current-supply system for efiecting initially reduced energization ofdevices such as electron tubes, comprising a current-supply circuit, a current limiting impedance serially included in said circuit, whereby initially to efiect less-than-full energization of a supplied device, a ctu'rent-conducting 'U-shaped thermomotive member mounted atits ends on rigid supports fixedrelative to one another and serially included in said circuit to receive currentandrhavingone leg connected to one side'of said impedance, a normally-openswitch comprising a stationary contact rfixed relative to the ends of the 'U-shaped member and acontactcarried by said member at the bend :thereofforengagement with said stationary contact upon current activation of said member, and a connection between said stationary-contact .and .a point of said cir- Ycuit-on the side of said impedance opposite the side to which said member is connected, whereby the closing of said switch short'cireuits said impedance and said leg of the .U-shaped member, whereupon substantially full energizing current is supplied to the supplied device and said switch is'maintained in the short-circuitingposition by the heating effect generated in the other leg'of said 'U-shaped member by the increased current which flows therethrough, whereby the short circuited leg is cooler than the .other legand-whereby the cooler/leg partially counteracts the -forces acting on the hotter leg.

References Cited in the file of this patent UNITED STATES PATENTS 

